This invention relates to software tools for composing and editing documents. More particularly, it relates to methods, based on analysis of user inputs, for automatically selecting such tools.
While working with a paper document, a reader typically interacts with the document in two ways: 1) A narrow-point pen can be used to make handwritten notes in margins; and 2) a wide-tip highlight marker can be used to accentuate important text. A serious reader will generally have both tools at his disposal. In order to support this kind of interaction in an electronic reading/annotation device, a user is generally provided with a variety of editing tools (pens of various colors, highlighters, erasers, etc.), as well as a means of selectively activating one of those tools. Although a wide variety of tools may be available, most users will chose to interact almost exclusively with either a plain pen tool or a highlighter tool.
The most convenient type of electronic reading/annotation devices has a touch-pad combined with a display screen. Generally, the screen is a liquid-crystal display (LCD). Using a writing stylus provided with the unit, the user/reader may draw or write directly on the screen. The path of the stylus point on the screen may be recorded as a bit-mapped image. Alternatively, handwritten text may be converted to ASCII characters, and ASCII text, which the user desires to make prominent, may be tagged with a highlighting attribute.
Touch-pad display screens have found wide application in Personal Digital Assistants (PDAs), ultra-compact personal computers, with built-in operating systems, that are optimized for scheduling and other high-mobility operations. During the past several years, the popularity of PDAs has soared. Corporations such as Sharp, Casio, Philips, 3-Comm, and Hewlett-Packard have entered the fray. Most have flash memory, a small liquid-crystal-display touch-pad screen, a user input device which may be either a barely-usable, miniature keyboard, and/or a touch pad incorporated into the screen, as well as a communications port for transferring files between the PDA and a less-portable computer. A high-end PDA may incorporate a modem and communications software, as well as drawing, word-processing and spreadsheet software. A writing stylus, or xe2x80x9cpenxe2x80x9d, may be supplied, with which the user may write and draw on the touch-pad screen. The touch-pad feature has great utility on a PDA, as nearly all PDAs are too small to incorporate a keyboard that is large enough for touch typing. Thus, handwriting and drawings are stored as bit-mapped patterns. With writing recognition software that is supplied with many of the PDAs, a user""s handwriting can be converted to ASCII text. Compared with desk-top and lap-top computer systems, PDAs generally have very limited memory storage capabilities. However, the average amount of memory being supplied with PDAs is growing rapidly. Already, PDAs with 16 megabytes of flash memory are available. As it becomes possible to load an entire novel or textbook into the memory of a PDA, it is likely that they will find wide use as electronic editing and annotation devices.
Lap-top computers are equipped, almost exclusively, with LCD displays. Within the past year, flat screen displays utilizing LCD technology have become sufficiently inexpensive that they are beginning to replace cathode-ray-tube (CRT) displays used with desk-top systems. Because touch-pad functionality can be readily incorporated in an LCD display, it is likely that large numbers of both lap-top and desk-top systems will soon incorporate touch-pad functionality. With the availability of such systems, electronic editing and annotating of documents will become much more widespread.
What is needed is an automatic writing tool selection system for an electronic reading/annotation device that will eliminate the need for a user to explicitly select either a writing pen function or a highlighter marker function from a pallet of available graphic composition tools. The system should be fine tunable so as to better adapt to a particular user""s writing style, as well as to his editing and annotating needs. Additional desired features are that the selection process will be dynamic, and that highlighting strokes will be neatly redrawn by the system.
This invention constitutes a method, employable in connection with an electronic reading/annotation device, for automatically selecting between an electronic writing pen tool used for handwriting tasks and an electronic marker tool used for highlighting tasks. Whereas handwriting normally consists of small radius curves, and frequent changes of direction, highlighting strokes are normally long and smooth with hardly ever a change of direction.
The automatic selection method utilizes analysis of the shape of each pen stroke. More specifically, the length of each pen stroke is calculated dynamically between its starting and a later made point. If the length of the stroke is close to that of a straight line between the same two points and the stroke is longer than a typical handwriting stroke, the highlighting function is automatically selected. The exact determination of xe2x80x9cclosexe2x80x9d is a tunable parameter. Empirically, it has been determined that a stroke distance less that 110% of the straight-line distance serves well for the selection of the highlighting function.
In order to make the automatic selection process seemingly instantaneous, comparison of actual stroke length to straight-line length is made online, or on the fly. That is, the calculation commences as each new beginning stroke point is created, rather than offline at the end of each stroke.
An additional requirement may be placed on the user-made stroke before the highlighting function is selected. As a general rule, highlighting follows the lines of displayed text. As text is almost always displayed in a format consisting of horizontal lines, highlighting will normally follow one or more lines. However, some users may opt to place one or more vertical strokes before or after multiple lines of text as a highlighting shortcut. This is especially true if the use desires to highlight large sections of text. Thus, the user will normally intend that highlighting strokes be either horizontal or vertical, with respect to the display screen. As an additional enhancement to the selection method, highlighting strokes are conformed so that they are either perfectly horizontal or perfectly vertical.
In order to make the automatic selection process more robust, three other enhancements are made. Firstly, a determination as to whether or not the stroke is meant to be a straight line is delayed until straight-line distance has exceeded a set number of pixels. This feature recognizes the fact that handwriting includes many short, nearly-straight line sections, and that often, a written word may begin with such a section. Secondly, in order to prevent the online algorithm from needlessly flip-flopping between the pen and marker tools at the beginning of a stroke, the algorithm begins with the pen tool selected. The rationale for always starting with the writing pen is that it is the most commonly used writing tool.
Although the invention may be practiced most conveniently with an electronic stylus and a touch-pad screen, the invention may be employed with any pointing device, such a mouse, a trackball, or a touch-pad.